The print statement has long appeared on lists of dubious language
features that are to be removed in Python 3000, such as Guido's "Python
Regrets" presentation [1]. As such, the objective of this PEP is not
new, though it might become much disputed among Python developers.

The following arguments for a print() function are distilled from a
python-3000 message by Guido himself [2]:

print is the only application-level functionality that has a
statement dedicated to it. Within Python's world, syntax is generally
used as a last resort, when something can't be done without help from
the compiler. Print doesn't qualify for such an exception.

At some point in application development one quite often feels the need
to replace print output by something more sophisticated, like
logging calls or calls into some other I/O library. With a print()
function, this is a straightforward string replacement, today it is
a mess adding all those parentheses and possibly converting >>stream
style syntax.

Having special syntax for print puts up a much larger barrier for
evolution, e.g. a hypothetical new printf() function is not too
far fetched when it will coexist with a print() function.

There's no easy way to convert print statements into another call
if one needs a different separator, not spaces, or none at all.
Also, there's no easy way at all to conveniently print objects with
some other separator than a space.

If print() is a function, it would be much easier to replace it within
one module (just def print(*args):...) or even throughout a program
(e.g. by putting a different function in __builtin__.print). As it is,
one can do this by writing a class with a write() method and
assigning that to sys.stdout -- that's not bad, but definitely a much
larger conceptual leap, and it works at a different level than print.

The signature for print(), taken from various mailings and recently
posted on the python-3000 list [3] is:

def print(*args, sep=' ', end='\n', file=None)

A call like:

print(a, b, c, file=sys.stderr)

will be equivalent to today's:

print >>sys.stderr, a, b, c

while the optional sep and end arguments specify what is printed
between and after the arguments, respectively.

The softspace feature (a semi-secret attribute on files currently
used to tell print whether to insert a space before the first item)
will be removed. Therefore, there will not be a direct translation for
today's:

The changes proposed in this PEP will render most of today's print
statements invalid. Only those which incidentally feature parentheses
around all of their arguments will continue to be valid Python syntax
in version 3.0, and of those, only the ones printing a single
parenthesized value will continue to do the same thing. For example,
in 2.x:

Luckily, as it is a statement in Python 2, print can be detected
and replaced reliably and non-ambiguously by an automated tool, so
there should be no major porting problems (provided someone writes the
mentioned tool).

The proposed changes were implemented in the Python 3000 branch in the
Subversion revisions 53685 to 53704. Most of the legacy code in the
library has been converted too, but it is an ongoing effort to catch
every print statement that may be left in the distribution.